The present invention relates to open-end spinning or rotor spinning. Open-end spinning machines generally consist of a series of individual spinning units, aligned on the two fronts of the machine, each of which consists of a spinning rotor, which produces twisted thread starting from the singularized fibres of a sliver, and a collection unit which—after controlling the quality of the yarn with the interpositioning of a slubcatcher between the two components—causes the yarn to be wound onto a tube to form a bobbin. This bobbin is thus formed by pulling and winding the yarn onto its surface, as it is pulled in rotation by the underlying roll on which the bobbin in formation is resting. The yarn is spirally wound onto the bobbin in formation as the collection unit is provided with a thread-guide device which distributes the yarn with a backward and forward axial movement onto the outer surface of the bobbin.
The structure of the individual spinning station is illustrated in the scheme of FIG. 1, and its functioning is briefly described hereunder according to its normal operating mode.
Proceeding upwards, the single spinning station 1 consists of an actual spinning unit 2 and a collection unit 3, of which the main components which lead to the transformation of the sliver of parallelized fibres to the bobbin of wound yarn are briefly illustrated below.
The feeding tape or sliver S is contained in a cylindrical vase 4 which it is deposited with a double spiral. The sliver S is fed to the unit by a feeding roll 5 passing through the funnel-shaped conveyor 6 and reaches the card 7, a rotating roll equipped with a toothed washer which singularizes the fibres of the sliver S and sends them by suction to the spinning rotor 8, which operates in depression.
The singularized fibres are deposited by a centrifugal effect in the peripheral throat of the spinning rotor 8, which rotates at very high velocities (up to 150,000 revs/minute and over); from here they are collected and removed in the form of the thread F, axially leaving its central opening 9, receiving torsions by the rotation of the rotor itself in the course which runs between its internal throat and said opening 9, thus creating the twisted thread F.
The capturing of the thread is effected with a pair of opposite extraction cylinders 11 and 12 which seize the thread F and driven at a controlled rate according to the arrow a, thus causing the linear production of yarn, generally indicated in m/min. The quality-control sliver 14 of the yarn F can be positioned before the cylinders 11/12.
The thread F thus produced enters the collection unit 3, passes through a thread-presence sensor 15 and encounters a compensator 16 for compensating the variations in length of the run between the spinning unit 2 and the depositing point of the yarn F on the bobbin. The thread-guide device 21 distributes the thread on the bobbin in formation by transversally moving with a backward and forward movement according to the double arrow b, activated by a motor 20 which drives a longitudinal rod 22 in common with the other units of the spinning machine.
The bobbin 25 collects the thread F and is held by the bobbin-holder 26 equipped with two idle and openable counterpoints 27 which become engaged with the base tube 28 of the bobbin. The bobbin in formation 25 rests on its activation roll or collection cylinder 29.
Recently designed automatic open-end spinning machines are equipped with service trolleys which patrol the fronts of the spinning machine and effect the required interventions by stopping in front of the spinning unit which require them.
There are essentially three types of interventions required:                start-up, at the beginning of the spinning starting from the stopped spinning machine, activating it and subsequently positioning a new tube in each station, the starting being effected with reattachment with an auxiliary thread and winding the thread produced on the new tube to form a bobbin, after eliminating the section of auxiliary thread;        reattachment, when the yarn is interrupted for any reason, without having reached the length established for completing the bobbin, using the yarn already produced from the side of the bobbin, reattaching and restarting the winding on the same bobbin. The reattachment procedure consists, in its essential lines, in the opening, cleaning and closing of the rotor, the preparation of the sliver end, capturing and preparation of the skein-end on the side of the bobbin, restarting of the rotor and feeding, re-introduction of the prepared skein-end in the rotor, re-extraction of the skein-end connected to the newly produced thread by rewinding it in the collection unit. The cleaning cycle programmed is equivalent to the reattachment cycle, caused with a controlled breakage of the thread;        removal, after reaching the length required for completing the bobbin. After stopping the bobbin, a final thread reserve is deposited on the tip of the tube, which allows the skein-end or top of the bobbin yarn to be easily identified and removed, in the subsequent use of the bobbin in operations effected downstream, for example weaving. The present invention is directed in particular to this operation. The finished bobbin is unloaded and the start-up of the unit is then effected as described above, for the production of a new open-end bobbin of yarn.        
These interventions are generally effected by separating the bobbin 25 from its activation cylinder 29, stopping its movement and allowing the activation of the bobbin 25 or its tube 28 to be effected by an auxiliary activation roll situated on board the service trolley.
In the field of intervention and devices and procedures of automated service trolleys for open-end spinning machines, the applicant is the holder, among other patents, of the following patents IT 1,146,694, EP 340,863, EP 443,220, EP 473,212, IT 1,258,220, IT 1,258,221, IT 1,258,222, EP 1,524,230 A2.
The automation trolley generally consists of a moveable structure along the fronts of the machine, a communication system with the central control unit of the spinning machine and with the spinning units which form the machine, a translation and stopping system of the trolley in front of the units which require the intervention. The moveable structure carries both its control unit and the specific organs or groups of organs for single or multiple operations of the various cycles, which can be required each time and are managed by said control unit.
The present invention can refer to the service trolleys described and claimed by the same applicant in its European patent application EP 1,524,230 A2, to which reference should be made for its structure and essential components.